Rules for Nikoli Puzzles: Introduction

To keep my introduction brief, let me just say that I've been a fan of
Japanese pencil puzzles, particularly the ones created and/or published by
Nikoli (English page) since early
2007, and own a variety of these puzzle books (here's
my inventory). However, it's not always easy to find
descriptions of the rules in English, especially for less popular or less
well-known games. I've created this page to help solve that problem, by
adding rules for new-to-me puzzles as I see them and figure out how to solve
them. (I'm slowly working through a backlog of Nikoli's books.) Also, I'll
try to provide rules for some
special cases in books I own. Links to each
summaries of each puzzle's rules are below, followed by some more intro
details (if you're interested).

Here's some more detail on the rules posted here. Most of these come from:
(1) English instructions from Nikoli when available, e.g., from
Nikoli Puzzles in English
or the Penpa series of books;
(2) other English instructions available, e.g., at
at Nikoli on Wikipedia and
Wikipedia's List of Nikoli Puzzle Types;
(3) automatic/computer translations (e.g., using
Babel Fish or
Google Translate) of Japanese
instructions, preferably Nikoli's, e.g., from
Nikoli Puzzles in Japanese
or Nikoli books themselves; and (4) my own interpretation of the rules by
trial and error, often using sample solved puzzles in books I own to help.
Given that 1 and 2 are often limited, most of the rules here come from 3 and
4 combined, typically by using the Google Translate app on my phone with
rules in Nikoli books I own to get English rules that I clarify as needed
based on past experience with translated rules and through trial-and-error
on actual puzzles and their solutions in the books.
Puzzles that appear to require knowledge of the Japanese language will be
omitted, but ones using Japanese words/characters that can be solved without
knowledge of the language will be included.
If you can't find what you're
looking for here, you might also try
Nikoli-Puzzles [janko.at],
which has a similarly-sized list but categorizes puzzles by type (e.g.,
coloring cells or placing symbols).

Feel free to
e-mail me
if you find these short rules helpful or unclear, or if you can correct any
mistakes I may have made. And feel free to link to this page and/or point
others to it for basic Nikoli rule descriptions. Thank you very much for
any help you can provide. Special thanks to Grant Fikes and David Olmsted
for some rules clarifications/corrections (check out Grant's
Cleverly-Titled Logic Puzzle Blog
for hundreds of Nikoli-style puzzles he created), to hige_penguin on
Twitter for providing some translations and explanations, and to Otto Janko
for some title corrections. I will try to add more puzzle rules as I can,
so check back now and then for updates.

Nikoli Puzzle Rules Summaries

Akari / Light Up

Place light bulbs (circles) so that every square in the grid is lit or
contains a light bulb. Numbered cells indicate how many light bulbs are
next to it, horizontally and vertically. Light bulbs may go in any
white/empty cell and illuminate all the cells vertically and horizontally
from it to a black cell or the edge of the board, whichever comes first, but
no light bulb may illuminate any other light bulb.

Amibo

Draw lines horizontally or vertically from marked/numbered cells, such
that the lengths of the line is equal to the number in the cell, only one
line connects to each numbered cell, each line crosses at least one
other line of the same length, and lines do not form closed loops. There
may be lines that do not connect to marked/numbered cells. Marked cells
without a number may have a line of any length.

Bag

Draw a single loop without crossings or branches along the grid lines.
Every numbered cell must be inside the loop. Numbered cells can see the
specified total number of cells vertically and/or horizontally (including
itself) before reaching a wall of the loop.

Barns

Draw a single loop without crossings or branches through the centers of
the cells in the grid, passing through every cell in the grid. Lines that
enter a gray area cannot change direction until the leave the gray area.
Lines are only allowed to cross inside the gray areas. Dark lines in the
grid are walls and cannot be crossed by the loop.

Capsule Place

Draw capsules (2x1 or 1x2 ovals, half white, half black) so that all
circles in the grid have at least one capsule half of the same color adjacent
to it vertically or horizontally, cells with an X have no capsule adjacent
vertically and horizontally, and long sides of capsules that touch each
other may not match in color.

Source: Google Translate of
rules in Puzzle Communication Nikoli 136 with some trial-and-error

Note: This title is tentative.

Chokona

Paint cells of the grid black so that black sections form squares and/or
rectangles, and numbered blocks contain the given number of black cells (not
necessarily consecutively/joined). Blocks without numbers can have any
number of painted cells. Squares and/or rectangles should not share
sides.

Combination Block

Draw blocks along grid lines so that each block contains one dotted line
within it, all blocks must fit together to completely fill the grid, blocks
are not squares or rectangles, and the same shaped blocks may not share
a side.

Source: Puzzle Communication Nikoli 131, Google translated rules

Note: This title is tentative, and since this puzzle seems to involve
more guessing and less logic than I like, I haven't really played through it
to test my interpretation of the rules.

Conveyor Belt

Draw arrows in the cells of the grid so that circled arrows (balls) are
directed to the "IN" cell. All arrows in a block point in the same
direction. Cells in a block that are not used are painted black, and
black cells cannot touch vertically or horizontally. All blocks must
be used in some way, and the path of one circled arrow (ball) may not flow
through another circled arrow (ball).

Country Road

Draw a single loop (road) through the grid where the line passes
horizontally or vertically through the center of cells without crossing,
branching, or going through the same cell twice. Countries (bold outlined
areas in the grid) with numbers have the given number of cells used by the
road, and countries without a number must have 1 or more cells used by the
path. The road may only enter a country once and exit it once. Adjacent
unused cells must not be in different countries.

Cross Counter

Draw lines along the dotted lines of the board grid to divide it into
squares such that numbers in cells indicate the number of corners of that
cell where drawn lines cross.

Source: Google Translate of
rules in Puzzle Communication Nikoli 136 with some trial-and-error

Note: This title is tentative.

Dosun-Fuwari

Place balloons (white circles) and iron balls (black circles) into the
grid so that each room (bold bordered area of the grid) contains one balloon
and one iron ball. Balloons are light and float, and thus must be placed at
the top, immediately under black cells, or under other balloons. Iron balls
are heavy and sink, and thus must be placed at the bottom, immediately above
a black cell, or above other iron balls.

EisBahn

Draw a single loop through the grid from IN to OUT that follows the
directions of the arrows. Lines that enter a gray area cannot change direction
until they leave the gray area. Lines are only allowed to cross inside the
gray areas. The loop must go through every gray area at least once.

Erue Ichiru

Place L-shaped blocks of 3 cells each in the grid so that they cover the
kanji correctly (what looks like one symbol is the corner, what looks like
two side-by-side is the end, question marks can be either), and all white
cells are connected (the black cells do not divide the board).

Fillomino

Fill in all empty cells by dividing the grid into blocks (groups of cells
connected horizontally and/or vertically with the same number) so that each
block has the same area/size as the number in it and blocks of the same
size do not touch each other horizontally or vertically.

Five Cells

Divide the grid into blocks of exactly 5 cells (connected horizontally
and/or vertically) by drawing along the grid lines . Numbers indicate how
many block edges, including the puzzle border, surround the cell, and
a block may have up to five numbers in it.

Source: Penpa 2012 and translation by hige_penguin

Goishi Hiroi / Go Stones

Starting from any stone on the board, travel in vertical and/or
horizontal lines to pick up all of the go stones by numbering the order in
which they are removed from the board. You may only change direction when
you pick up a stone, but may not go back in the direction from which you
came, and if you travel over a spot where a stone was picked up (numbered),
you may not change direction at that point (the stone is no longer present).
P.S. -- It looks like more than one solution may exist for these puzzles.

Hanaregumi

Place one number in every room (bold outlined areas in the grid), where
the number is equal to the number of cells in the room, so that the number
of empty (white) cells between a number and the next closest one both
vertically and horizontally equals the difference between the two
numbers.

Source: Google Translate of
rules in Puzzle Communication Nikoli 134 with some trial-and-error

Hashiwokakero / Bridges

Connect all of the islands together by drawing bridges vertically or
horizontally between them. The number on each island indicates the number
of bridges connected to that island, there can be no more than two bridges
connecting a pair of islands, and the bridges may not cross each other.

Hebi

A snake is the numbers 1 (head) to 5 (tail) sequentially connected
vertically/horizontally. Place snakes in the grid so that no two snakes
touch each other (share a side), and no snake can "see" any part of another
snake (i.e., for a given snake, from the 2-to-1 direction, no other snake's
parts can be between its 1 (head) and a black cell / puzzle edge). Black
cells with numbers and arrows indicate the snake part number in the adjacent
white cell in the arrow's direction; a 0 means there is no snake part from
that black cell to the next black cell or puzzle edge.

Source: Penpa 2011, Penpa 2012, and translation by hige_penguin

Herugolf

Move all circles (hit all balls) at least once to bring them to a cell
marked H (the holes), one circle to every H, by drawing an arrow vertically
and/or horizontally through the cells for each hit. Arrows may not cross
other arrow lines, circles, or H cells. Numbers in circles indicate the
number of cells it travels on the first move; this decreases by 1 after
every move, and the direction of movement can only change at the end of
a move. The circle must stop when the number is reduced to 0 or it reaches
an H cell. Circles may not move outside of the grid, and cannot stop in the
gray areas (water hazards).

Heyawake

Paint cells black in each room (bold outlined areas in the grid) so that
rooms with a number have that many painted cells in them, painted cells are
not connected, white cells are not separated by painted cells, and white
cells do not span more than two rooms in a straight line.

Hiroiiya

Draw lines horizontally or vertically through the centers of the cells to
connect each number with a G (goal). The numbers show how many circles the
line must pass through, and the direction of the arrow in a numbered cell
shows the starting direction for the line.

Source: Puzzle Communication Nikoli 119 with trial-and-error.

Hitori

Paint cells black such that numbers appear no more than once in each row
and column. Painted cells must not touch horizontally or vertically, and
white (unpainted) cells must create a single connected area not separated by
painted cells.

Honke Yajitatami

This is basically the same as Yajitatami, but
shaded cells can't be subdivided and they also serve as borders. So draw
lines along the grid lines to divide the board into 1 by X (X = 2+)
rectangular rooms (the tatami mats) where numbers indicate the size of the
room (number of cells) and arrows indicate the number of rooms in the
direction of the arrow, up to shaded cells or the outer border of the board
(whichever comes first). There is always a line / room border directly in
front of an arrow, and four rooms may not share a single corner.

Source: Puzzle Communication Nikoli 137 with trial-and-error.

Note: This title is tentative.

Hotaru Beam

Draw lines in the grid to create a single, connected network joining all
circles (on intersections of grid lines). The network may cross or branch
only at circles. Dots on circles indicate where a line of the network
connects to the circle. Numbers in circles indicate the number of turns the
line makes after leaving the dot and connecting to another circle.

Hukumenzan

Each different character in the equation represents a different number.
Replace the characters with numbers to solve the equation. Zero will not be
a leading digit, and numbers that appear in the equation may also be used as
a character.

IceLom

Draw a single loop through the grid from IN to OUT that passes through
all white cells, passing through all numbered cells in numerical order.
Lines that enter a gray area cannot change direction until they leave the
gray area. Lines are only allowed to cross inside the gray areas. The loop
must go through every gray area at least once.

Note: this appears to be very much like Ice Barn, but following numbers instead of arrows and the path must go through all white cells.

Ichi Honsen

Draw vertical and horizontal lines through the centers of cells in the
grid so that the lines in each row and column are of different lengths and
the total length of lines passing through numbered cells equals the number
in the cell.

Source: Google Translate of
rules in Puzzle Communication Nikoli 137 with some trial-and-error

Note: This title is tentative.

Inshi no Heya

Fill all the cells in the grid with numbers from 1 to 9, inclusive, such
that no number appears twice in any row or column and the product of the
digits in each room (bold outlined areas in the grid) equals the given number
in each room.

Ittouryoudan

Draw one straight, unbending line of any length along the grid lines to
divide the field into two pieces of equal area.

Source: Puzzle Communication Nikoli 120 with trial-and-error.

Juosan

The grid is divided into territories by bold lines. Fill in all cells
with a vertical or horizontal dash so that the numbers in territories equal
the number of either vertical or horizontal dashes in it (in some cases,
there may be equal numbers of both). Horizontal dashes can extend more than
three cells horizontally but no more than three cells vertically, and
vertical dashes can extend more than three cells vertically but no more than
three cells horizontally.

Kaero

Move letters on the board so that each room (bold outlined areas in the
grid) contains all appearances of one letter -- all of the As are in one room,
all of the Bs are in another room, etc. Movement of letters is indicated by
lines that pass through the centers of boxes, bending at right angles as
needed, with an arrow at the end indicating the destination cell. Lines
cannot cross or branch.

Kaitouranma

Draw straight lines on the puzzle grid, from border to border, to divide
the grid into partitions. Each partition must contain at least 1 white
circle, or at least 1 black circle, but cannot contain both black and white
circles.

Note: the name of this puzzle means "cutting the Gordian knot".

Source: translation by hige_penguin

Kakuro / Cross Sums

Place a number from 1 to 9, inclusive, in each cell so that the sum of
the numbers in each block (vertical column or horizontal row of connected
white cells) is equal to the number at the top or left of that block cells
and each number is used no more than once in each block.

Kanaore

Fill the grid with the given (Japanese) words. Each word has a number and
direction; the word starts in the matching numbered cell in the grid and
begins extending the direction specified. Each letter/character must be placed
horizontally or vertically adjacent to the last. Some letters/characters may
be used by more than one word.

Keisuke

Basically a number crossword where you have to supply the black cells.
Place numbers from clues in the grid (across = left to right, down = top to
bottom) where number edges meet the puzzle edge or a painted black cell.
Black cells may not touch horizontally or vertically, and all white cells
must create a single connected area not separated by black cells.

Source: translation by hige_penguin

Kin-Kon-Kan

Place diagonal lines in cells (mirrors) such that each room (bold
bordered area in the grid) contains exactly one mirror, and letter-number
pairs at the edges of the grid can be connected by straight lines that
bounce of the same number of mirrors as the number in the letter-number
pair. For example, B2 at one edge must connect to the other B2 by straight
vertical and horizontal lines (passing through the centers of the cells)
that bounce off of 2 mirrors in the grid.

Source: Kin-Kon-Kan on Wikipedia (page has been deleted)

Knight Flow

Draw a single, closed loop without branches or crossings through the grid
that goes through all white circles, does not go through any black circles,
and goes through white triangles as needed (they're optional). The line
much alternate between moving to a vertically or horizonally adjacent symbol
and making a chess knight's move (2 squares vertically then 1 square
horizontally, or 2 squares horizontally then 1 square vertically).

Source: Google Translate of
rules in Puzzle Communication Nikoli 128 with some trial-and-error

Kurodoko (was Kuromasu) / Where Is Black Cells

Paint cells black such that each numbered cell can see the specified
total number of cells vertically and/or horizontally (including itself)
before reaching black cells or edges of the grid. Black cells may not touch
horizontally or vertically, and all white cells must create a single
connected area not separated by black cells. Numbered cells may not be
black.

Kurotto

Color cells in the grid black so that each circle with a number has that
number of consecutive black cells extending from it, vertically and
horizontally. There may be multiple lines of black cells extending from
a single circle, empty circles may have any number of black cells around
them, and cells with circles may not be colored black.

Kuroyunitto (Black Unit?)

Color non-circled cells in the grid black so that each numbered circle
has that total number of black cells connected to it vertically and
horizontally and unnumbered circles have an unspecified number of black cells
connected to it; in both cases, groups of black cells can bend, and all black
cells in a joined group count as connected to a number.

Source: Google Translate of
rules in Puzzle Communication Nikoli 138 with some trial-and-error

Note: This title is tentative.

L Route

Divide the grid into only L-shaped blocks 1-cell wide. Circles mark the
L's knees/corners (places where the Ls bend at a right angle), and arrows
indicate an end of an L and point towards the knee/corner. An L-shaped
block may have any number of cells in it (minimally 3 to create an L).

Line Line Poker

A 5x5 grid of playing cards is the board, and each row and column is
labeled with a poker hand (e.g., one pair, full house, straight). The suits
for all cards are given. Fill in the missing card numbers so that all rows
and columns have the type of poker hand specified. {Note: The rules I saw
provided graphic examples of the hand types, making translation from
Japanese fairly simple. I'm not sure if this description is clear enough,
but it should be easier to understand once you see this puzzle. I can try
to clarify if people request that though.}

Source: Puzzle Communication Nikoli 126

LITS (was Nuruomino)

Color four consecutive squares (tetrominoes) in each area surrounded by
bold lines such that similarly shaped or rotated tetrominoes do not touch
except possibly at corners, the colored squares form a single connected
area, and the colored squares do not form areas of 2x2 or larger.

Loop de Route

Draw one or more closed loops along the grid lines through circles with
the same number. Circled numbers indicate the number of times a line
turns/bends before reaching the next circled number of the loop. Loops may
not branch, but they may cross each other.

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative and the Japanese appears to be "ruupu do
ruuto", which I think is the equivalent of "loop de route".

Machigai Sagashi

A find-the-differences puzzle -- locate parts of the given pictures that are not the same in both.

Makaro

The grid is divided into rooms by bold lines. Fill all empty cells with
numbers so that each room has numbers 1 through the number of cells it
contains, and numbers in one room may not be adjacent to the same number in
another room. Black cells with arrows point to the vertically or
horizontally adjacent cell with the largest number of those (up to) 4 cells
surrounding it.

Makkuro / Makuro

Fill the crossword-like grid with numbers according to the given clues,
which are numbered and grouped by answers that read across (left to right
horizontally) and answers that read down (top to bottom vertically).
Clues are given in terms of the answers to other clues; for example, using
a sample game from Nikoli, 1 down minus (ひく) 8 across,
1/2 (2分の1) of 4 down, 7 down times (倍) 8,
2 across plus (たす) 6 down. For puzzle clues using Japanese
words, treat the words as variables and all clues as multiplications -- if
there's no number in the clue, then it's 1, just the word/variable itself.
This wasn't too hard to understand once it was explained to me, but if
I didn't explain it well here, let me know.

Masyu

Draw a single loop without crosses or branches with lines extending
horizontally or vertically through the centers of the cells. The loop must
include all cells with white and black circles. White circles indicate that
the path goes straight through the cell and makes a 90-degree turn in the
cell before it, the cell after it, or both. Black cells indicate that the
path makes a 90-degree turn inside the cell, with the path extending
straight for two cells before and after it.

Mochikoro

Paint cells black to create rectangular and/or square rooms of white
cells with at most one number per room and size/area equal to the number
in each room. Rooms may not touch vertically or horizontally, but must
touch at least one other room diagonally so that all rooms are connected.
Black cells may not form areas of 2x2 cells or greater.

Source: Mochikoro on Wikipedia (page has been deleted);
clarification by Grant Fikes

Moon-or-Sun

Draw a single loop through the grid where the line passes horizontally or
vertically through the center of cells without crossing, branching, or going
through the same cell twice. The line can only go through each dark bordered
room in the grid once (no re-entering after leaving), must go through all
sun symbols or all the moon symbols in the room (but not both), and the line
must alternate going through suns and moons in rooms (if it goes through
moons in one room, it must go through suns in the rooms before and after it).

Mushikuizan

Each square in the equation represents a single digit, 0-9. Replace the
squares with numbers to solve the equation. Zero will not be a leading
digit, and numbers that appear in the equation may also be used in the
square(s).

Nagareru

Draw a line horizontally, vertically, or turning through the centers of
cells to create a single, continuous loop in a direction that does not cross
itself, branch off, or go through the same cell twice. The line must go
through cells with black arrows, and these arrows indicate the direction of
the loop. White arrows in black cells indicate a wind blowing in the given
direction until it reaches another black cell or the grid border; the loop
line may not move into this wind. When a line enters a cell where the wind
is blowing from the side, it must turn in the direction of the wind. The
line cannot hit the grid border or enter black cells.

Nagenawa

Draw any number of square and/or rectangular loops in the grid, using
vertical and horizontal lines through the centers of the cells, such that
blocks with numbers contain line segments in the given number of cells of
that block. Loops may cross in any cell, but cannot share line segments and
cannot change direction at a crossing. Some loops may be completely
separate from others (not crossing any other loops).

Nansuke

Place all of the given numbers into the crossword-like grid. (This is
like a crossword with numbers, where you have all the answers and have to
figure out where they belong, instead of knowing where the answers belong
and having to figure them out.)

Noridoko

Paint cells black such that each numbered cell can see the specified
total number of cells vertically and/or horizontally (including itself)
before reaching black cells or edges of the grid. Black cells must form 2x1
or 1x2 areas, and these areas may not touch horizontally or vertically. All
white cells must create a single connected area not separated by black
cells. Numbered cells may not be black.

Note: this seems like kuromasu/kurodoko, just with 2x1 and 1x2 black
areas instead of 1x1 black cells, but I may be missing something.

Norinori

Paint cells black such that each block contains two black cells with
black cells forming 2x1 or 1x2 areas that may not touch horizontally or
vertically. Note that the black cell pairs may cross the bold block
borders.

Source: Penpa 2011

Number Link

Connect pairs of the same number together with lines that pass
horizontally and/or vertically through the centers of cells. Lines cannot
cross or branch off, and cannot go through the same cell twice.

Nurikabe

Paint cells black so that the grid is full of white areas, each with
a single number and size equal to that number, separated by black cells
(walls) that are all connected and do not form 2x2 or larger areas.
Numbered cells must not be painted black, and white areas must be separated
from each other horizontally and vertically by black walls.

Nurimeizu

The grid is divided into rooms by bold lines. Create a maze that goes
from S to G across only white cells by coloring cells black to make walls.
All cells in a room must be either black or white. All white cells must
remain connected, but cannot form a loop. Neither white not black cells can
form 2x2 or larger squares. Rooms with S, G, circle, and triangle cannot be
painted black; all of the cells in the room with the circle will be on the
shortest path from S to G, but none of the cells in the room with the
triangle will be.

Odoroku Nakare

Place 1x2 or 2x1 all-white and/or all-black tiles in the gird such that
cells of the same color do not share a side, all tiles including 1x1 given
tiles are connected vertically and/or horizontally, and a 1x2/2x1 tile may
not form a straight line with a 1x1 tile. Four tiles are allowed to meet at
a single corner.

Source: Puzzle Communication Nikoli 135 with trial-and-error.

Note: This title is tentative.

Okiwake

Put one or more numbers in each room (bold outlined in the grid) such
that the numbers sum to the room's size (number of cells), numbers are not
repeated in the same row and column, and each number in each room must
connect vertically and/or horizontally to at least one number in another
adjacent room.

Source: Puzzle Communication Nikoli 135 with trial-and-error.

Note: This title is tentative.

Orikusu / OLIX

Draw a single closed loop of vertical and horizontal lines through the
centers of grid cells such that cells marked: "O" have no lines through
them, "L" have lines that bend in them, "I" have lines that go straight
through them, and "X" have lines that cross (vertically and horizontally).
Lines cannot cross in a cell other than those marked "X".

Panelize

The puzzle name is Paneraizu in romaji, which I'm taking to be Panelize.
Draw vertical and horizontal lines along the grid lines to divide the grid
into square and rectangular regions. Circled numbers must be contained
within a square with side length equal to the number (e.g., a cell with
a circled 3 lies inside a 3x3 square region). Intersection points of the
grid lines may not have four drawn lines coming out from them (+s are not
allowed, but Ts are OK), and squares of the same area may not share
a side.

Source: Puzzle Communication Nikoli 127 with trial-and-error; I'm not
sure this description is completely correct, but it does seem to work with
the puzzles I've tried so far.

Pencils

Two parts: (A) Draw pencils in the grid, straight lines of 1+ cells with
a triangular tip at one end. If a pencil contains 1+ numbers, it must have
the same length as the number(s). (B) Draw lines from the tips of each
pencil through the centers of cells, vertically, horizontally, and optionally
turning. The line must go through as many cells as the number in the pencil
(if present), and pencil lines cannot branch or cross. Note: The cell with
a pencil tip does not count as one cell when drawing lines.

Purakansu

Fill the grid with spelled-out numbers so that where a number is given at
an intersection, the spelled-out numbers that cross there sum to the given
number. Note that the rules provided specify how certain numbers should be
written, and (in my experience) Japanese numbers typically use a format of
number * power of ten. So for example, 234 would be spelled like 2 100 3 10
4. If I've made some mistake here, hopefully someone with more Japanese
knowledge can correct me.

Reflect Link

Draw a single loop without branches by drawing lines horizontally and/or
vertically through the centers of cells. If a cell has a plus sign in it,
two lines intersect in it; these are the only places lines may intersect.
Cells with triangles in them reflect the line at right angles, and all
triangles must be touched by the lines. Numbered triangles indicate the total
number of cells (including the triangle's cell) that the beam travels
horizontally and vertically before changing direction.

Ring Ring

Draw square and/or rectangular hoops (rings) through the centers of grid
cells such that lines go through all open/white grid cells. Hoops are
allowed to overlap and cross each other, but they may not touch at a single
corner.

Source: Puzzle Communication Nikoli 135 with trial-and-error

Note: This title is tentative.

Ripple Effect

Number all cells in each room (bold outlined areas in the grid) such that
each room contains consecutive numbers starting from 1, and if a number
appears more than once in a row or column, they are separated by at least
that number of cells. For example, a room with 4 cells must contain the
numbers 1, 2, 3, and 4, and two 3s in the same row must be separated by 3 or
more cells.

Roichima

Fill all cells in the grid with arrows that point up, down, left, and
right such that all arrows within a black-bordered room point in different
directions, and following the path of the arrows from each cell will end at
the black circle(s).

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative.

Rukkuea

Shade cells in the grid black to form squares that do not share sides.
Numbered cells indicate how many cells of the numbered cell itself, and the
four cells immediately adjacent vertically and horizontally are shaded
black. Shaded squares of the same size cannot follow each other in the same
row or column (they can repeat later if a different size square comes
between them).

Source: Google Translate of
rules in Puzzle Communication Nikoli 136 with some trial-and-error

Note: This title is tentative.

Sashigane

Divide the grid into only L-shaped blocks 1-cell wide. Circles mark the
L's knees/corners (places where the Ls bend at a right angle), and a number
in a circle indicates how many cells are in the L containing it. Arrows
indicate an end of an L and point towards the knee/corner. An L-shaped
block may have 0-3 marks (arrows and circles, numbered or not) in it.

Source: Penpa 2012 and translation by hige_penguin

Seek Words

Select Equation

Select one item from each column of the grid to create correct
mathematical equations. Each item can be used only once, and in a grid of
X rows, the selections must be made so that there are X correct
equations.

Shakashaka

Place black "triangles in squares" in white cells of the grid such that
parts of the grid remaining white always form a rectangle or square.
Numbers indicate how many black triangles are around the cell, vertically
and horizontally.

Source: Penpa 2011, Penpa 2012

Shikaku / Divide by Box

Divide the grid into rectangles and/or squares (boxes) such that each box
drawn contains one number and that number is the size (area) of the
block.

Shimaguni

Shade in a polyomino in each area surrounded by bold lines such that no
two polymoinoes touch except possibly at corners, no two touching regions
contain polyominoes of the same size, and a numbered region contains
a polyomino of that size.

Shirokurodo

Place 1x2/2x1 tiles in black and white horizontally and vertically in the
grid without overlapping each other or existing cells. Tiles of the same
color may not share a side, and numbers indicate the number of tiles in the
four adjacent cells (up, down, left ,right). All placed and existing tiles
must be connected, and they cannot form any 2x2 blocks.

Source: Google Translate of
rules in Puzzle Communication Nikoli 137 with some trial-and-error

Note: This title is tentative.

Skeleton Puzzle

Place the given words into the empty (skeleton) grid so that all of the
words link up crossword-style. A word of X characters must go into
a horizontal or vertical line of exactly X characters.

Sphere/Queue Stone

Move balls in the grid horizontally only, not passing through walls (bold
vertical grid lines), so that numbers indicate how many cells without balls
are between it and the floor (bold horizontal grid line) in the same column.
Motion is indicated by arrows that cannot hit or cross any other arrows or
balls, and not all balls are required to move.

Source: Google Translate of
rules in Puzzle Communication Nikoli 136 with some trial-and-error

Note: This title is tentative.

Slalom (Suraromu)

Draw a single loop without crossings or branches by drawing lines
horizontally and/or vertically through the centers of cells, starting and
ending at the circled number, which indicates the total number of dashed
lines (gates) on the board. The loop must pass perpendicularly once through
each gate, numbered gates indicate the order in which the gates are
passed, unnumbered gates may be crossed in any order, and each gate may be
crossed only once. If a numbered black cell is next to more than one gate,
then the number refers only to the gate which has that same number on both
ends.

Slither Link

Draw a single loop without crossings or branches by connecting adjacent
dots with horizontal or vertical lines. If a cell has a number in it, then
it must have exactly that number of lines surrounding it. If a cell is
empty, then it may have any number of lines (from 0 to 3).

Stained Glass

Paint areas black according to the rules indicated by the color of the
circles at their intersection: a black circle means more of the neighboring
areas touching it are painted than unpainted; a white circle means more of
the neighboring areas touching it are unpainted than painted; a gray circle
means there are an equal number of painted and unpainted neighboring areas
touching it.

Sto-stone

Color in cells in the grid black so that each dark bordered room in the
grid with a number contains that number of continuous black cells (no number =
no black cells). Black cells cannot connect across rooms, vertically or
horizontally, and when all the black cells (stones) are "dropped" straight
down, they completely fill the bottom half of the grid (at this point, they
are allowed to cross room borders).

Sum Line

Place a one-digit number from 1 to 9 in every white cell, where numbers
given as clues are the sums of the rows/columns. X cells between black
cells / puzzle edges are treated as X-digit numbers. The same one-digit
number may not be repeated in a row or column.

Source: translation by hige_penguin

Suukoroheya

Place one or more of the numbers 1, 2, 3, and 4 into each black-bordered
room of the grid so that each digit touches that number of other digits
vertically and/or horizontally, each room has all cells either empty or
filled with numbers, and all numbered cells are connected together.

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative.

Tasukuea

Paint cells of the grid black so that black sections form squares and
cells with numbers in squares touch squares with total areas equal to the
given number. A cell with a square but no number may touch any number and
size of black cells greater than zero. All white cells must create a single
connected area not separated by black cells. Cells with squares remain
white.

Tatamibari

Divide the grid into rectangles and/or squares (boxes) such that each box
contains one symbol (+, -, or |), boxes with a + are square (height and
width are equal), boxes with a - are wider than they are tall, boxes with
a | are taller than they are wide, and no four boxes share the same
corner.

Tatebo-Yokobo

Place a vertical or horizontal line through the center of every cell such
that shaded numbered cells have the given number of horizontal and/or
vertical lines extending out of it and unshaded numbered cells have a line
with length equal to the given number passing through it horizontally or
vertically.

Tentai Show

Divide the grid into blocks (groups of cells connected horizontally and/or
vertically with the same number) so that each block contains a circle, and the
block is symmetric under a 180-degree rotation about the circle (the shape
looks the same if you rotate it 1/2 turn). Blocks with black circles are
then painted black, while blocks with white circles are left unpainted.
The result should be a picture.

Tile Paint

Paint cells black in the grid such that each row and column has a total
number of painted cells equal to the number at the left and top of the grid.
Blocks in the grid (bold outlined areas in the grid) must be either fully
painted or fully unpainted. The result should be a picture.

Source: Nikoli Puzzle Cyclopedia

Toichikai

Place one arrow pointing up, down, left, or right in each bold-bordered
room of the grid so that each arrow points to one other arrow that points at
it and there is at least one room's worth of empty cells along the line of
sight between arrow pairs.

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative.

Tooi

The kanji 上 (up), 下 (down), 左 (left), 右
(right) indicate that white cells extend in that direction more than the
other three directions. Cells with a kanji character will not be painted
black. Black cells cannot touch each other vertically or horizontally.

Source: translation by hige_penguin

Tsura Tsura

Place integers >= 1 in all white squares so that each number appears
once in a row, column, and room, and that the numbers in each row, column,
and room are consecutive (but need not appear in consecutive order).

Source: Google Translate of
rules in Puzzle Communication Nikoli 137 with some trial-and-error

Note: This title is tentative.

Wa-suu Nori

Divide the grid into 1x2 or 2x1 rooms where each cell contains a number,
every row and every column must contain the numbers 1 through the number of
rows/columns, and the circled numbers indicate the sum of the numbers in each
room.

Source: Google Translate of
rules in Puzzle Communication Nikoli 138 with some trial-and-error

Note: This title is tentative.

Warp Hole

Place two circles (warp holes) in each room in the grid. "Spirits" will
move from the numbered cells in the direction of the arrows. When a sprit
enters a warp hole it immediately jumps to the other hole in the same room
and continues moving in the original direction. The numbered cells indicate
how many warps the spirit leaving that cell makes before it reaches the grid
border or a black cell. All warp holes must have at least one spirit that
passes through them; i.e., there can be no unused warp holes.

Source: Google Translate of
rules in Puzzle Communication Nikoli 137 with some trial-and-error

Note: This title is tentative.

Yagi to Ookami

The puzzle name means Goats and Wolves. Draw vertical and horizontal
lines on the grid, going from one grid edge to any other grid edge (i.e., no
loops within the grid), optionally making right angle turns only where black
dots are located, to divide the grid into regions where each region contains
only goats or only wolves (not both, and not empty). Lines may cross each
other anywhere in the grid except at the black dots.

Yajilin

Draw a single loop through the grid where the line passes horizontally or
vertically through the center of cells without crossing, branching, or going
through the same cell twice. The line cannot pass through numbered cells,
which indicate how many black cells are in the direction of the arrow in
that cell, or black cells, which cannot touch each other horizontally or
vertically. Every cell the loop doesn't pass through must either be a
numbered clue cell or a black cell.

Yajisan-Kazusan

Paint cells black such that numbered cells indicate the number of black
cells in the direction of the arrow in those cells. Black cells may not
touch horizontally or vertically, and all white cells must create a single
connected area not separated by black cells. Numbered cells must be painted
black if they contain false clues, but numbered cells painted black do not
necessarily contain false clues.

Yajitatami

Draw lines along the grid lines to divide the board into 1 by X (X = 2+)
rectangular rooms (the tatami mats) where numbers indicate the size of the
room (number of cells) and arrows indicate the number of rooms in the
direction of the arrow. There is always a line / room border directly in
front of an arrow, and four rooms may not share a single corner.

Source: Puzzle Communication Nikoli 135 with trial-and-error.

Note: This title is tentative.

Yosenabe

Draw vertical and/or horizontal arrows in the grid to move all numbered
balls into gray pots such that the drawn arrows do not cross or branch and
the sum of the numbers on the balls equal the number in the gray pots. If
a gray pot has no number, there must still be at least one ball placed in
it.

Source: Puzzle Communication Nikoli 135 with trial-and-error.

Note: This title is tentative.

Zabuton

Place integers in the cells so that the sum of all integers in each
black-bordered room of the grid equals the area of (number of cells in) that
room, the same numbers do not touch vertically or horizontally, and all
numbers are connected together.

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative.

Special Rules

Penpa Mix 5: 20 Puzzle Consecutive Attack

Here I briefly describe how these 20 puzzles are connected so that you
will (hopefully) be able to solve them all and get to the final answer.
The basic procedure, after solving the first puzzle and answering a question
about it, is to use the previous puzzle's answer to help solve the current
puzzle and answer a question about the current puzzle, which gets used to
solve the next puzzle, etc. As with my rules above, please let me know if
there are any mistakes here. Thanks, and thanks (again) to Grant Fikes for
help and corrections.

Kakuro -- Answer A is the number in the
outlined cell of the solved puzzle.

Slither Link -- Replace "A" in the
puzzle with the number from Answer A. Answer B is the total number of
3s inside the loop of the solved puzzle.

Nurikabe -- Replace "B" in the puzzle with
the number from Answer B. Answer C is the number of black cells in the
marked row of the solved puzzle.

Akari -- Replace "C" in the puzzle with the
number from Answer C. Answer D is the number of light bulbs in the
marked row of the solved puzzle.

Yajilin -- Replace "D" in the puzzle with the
number from Answer D. Answer E is the total number of black cells in
the solved puzzle.

Ripple Effect -- Replace "E" in the
puzzle with the number from Answer E. Answers F and G are the numbers
in the outlined cells marked as F and G.

Number Link -- Replace "F" and "G" in the
puzzle with the numbers from Answers F and G. Answer H is the number of
bends in the line connecting the two 4s in the solved puzzle.

Masyu -- If the number for Answer H is odd,
then replace "H" in the puzzle with a white dot. If the number for
Answer H is even, then replace "H" in the puzzle with a black dot.
Answer J is the number of white cells in the marked column of the
solved puzzle.

Fillomino -- Replace "J" in the puzzle with
the number from Answer J. Answer K is the number in the outlined cell
of the solved puzzle.

LITS -- Solve the puzzle, then count how many
times each shape (L, I, T, and S) appear in the solution. All rotations
and reflections of a given shape are added together. Answer L is the
letter of the shape that appears Answer K times.

Hitori -- Letters LITS in the puzzle are
solved by blacking out the one letter matching Answer L and leaving the
other three white. Answer M is the number of black cells in the marked
row of the solved puzzle.

Heyawake -- Replace both "M"s in the puzzle
with the number from Answer M. Answer N is the total number of rows
that contain 3 black cells in the solved puzzle.

Akari -- Replace "N" in the puzzle with the
number from Answer N. Answer P is the total number of light bulbs in
the solved puzzle.

Kakuro -- Replace both "P"s in the puzzle with
the number from Answer P. Answer R is the number in the outlined cell
of the solved puzzle.

Yajilin -- Replace "R" in the puzzle with the
number from Answer R. Answer S is the number of black cells in the
marked row of the solved puzzle.

Nurikabe -- Replace "S" in the puzzle with
the number from Answer S. Answer T is the number of black cells in the
marked column of the solved puzzle.

Number Link -- Solve the puzzle, then
count the number of bends in each line. Answer U is the number for
which the line joining them has Answer T bends.

Slither Link -- Replace all 4 "U"s in
the puzzle with the number from Answer U. Answer V is the total number
of 1s inside the loop of the solved puzzle.

Fillomino -- Replace "V" in the puzzle with
the number from Answer V. Answer W is the number in the outlined cell
of the solved puzzle.

Heyawake -- Replace "W" in the puzzle with
the number from Answer W. The final answer is the hiragana characters
left white (not shaded black) in the solved puzzle, read from top to
bottom and left to right.

Penpa Mix 6: 20 Puzzle Consecutive Attack

Here I briefly describe how these 20 puzzles are connected so that you
will (hopefully) be able to solve them all and get to the final answer.
The basic procedure, after solving the first puzzle and answering a question
about it, is to use the previous puzzle's answer to help solve the current
puzzle and answer a question about the current puzzle, which gets used to
solve the next puzzle, etc. As with my rules above, please let me know if
there are any mistakes here. Having gotten this from computer translations
with a bit of guess-work, things might not be completely right, but should
still enable you to get through them all. Thanks!

Ripple Effect -- Answer A is the number
in the outlined cell of the solved puzzle.

Nurikabe -- Replace "A" in the puzzle with
the number from Answer A. Answer B is the shape of the island in the
rightmost column containing the "4".

LITS -- Answer C is the number of shaded
tetrominoes in the puzzle of the same shape (in any rotation and/or
reflection) as Answer B.

Kakuro -- Answer D is the number of times
Answer C's number appears in the solution.

Akari -- Replace "D" in the puzzle with the
number from Answer D and solve the puzzle.

Masyu -- Copy the lights from Q5's solution
into the grid as white circles and solve the puzzle. Answer E is how
many cells in the column indicated by the arrow are empty (do not
contain part of the line solving the puzzles).

Heyawake -- Replace "E" in the puzzle with
the number from Answer E. Answer F is the number of black cells in the
column indicated by the arrow.

Fillomino -- Replace "F" in the puzzle with
the number from Answer F. Answer G is the number of 1s in the solved
puzzle, including givens.

Number Link -- Solve the puzzle treating
the L, I, T, and S cells as empty cells. Answer H is the letter crossed
by the line connecting the two numbers given by Answer G; if there are
2+ letters, the answer is the leftmost letter.

LITS -- Answer J is the number of pieces with
the same shape as Answer H, where all rotations and reflections of the
shape count as the same shape

Slither Link -- Answer K is the number of
times Answer J appears inside the closed loop of the solved puzzle.

Ripple Effect -- Replace "K" in the
puzzle with the number from Answer K. Answer L is the number that
appears the most in the row indicated by the arrow.

Yajilin -- Replace "L" in the puzzle with the
number from Answer L, and solve.

Future steps still in progress -- I do hope to post this eventually,
but it's not particularly high priority for me, and it will take some
time to interpret the automatic computer translations when I do get
around to it. Thank you for your patience.

The Monster Book of Logic Puzzles & Sudoku (a collection of Nikoli-made puzzles, but the book's not published by Nikoli)

The Ultimate 1001 Puzzle Book

Yubotu

Nikoli books I would like to get/buy, roughly in order of preference:

Puzzle Box 1, 4-5, 14+

Penpa 2020+

Puzzle Communication Nikoli 130, 165+

Marugoto series books

Penpagon

Camissimo (Nikoli original card game)

For reference, Puzzle Communication Nikoli is a quarterly publication coming
out every three months (in December, March, June, and September), Penpa 20xx
books come out every year (usually around November), and Puzzle Box
books seem to come out about every 2 years. I'm not sure about the rough
schedule of other types of books, but Nikoli's plans for the next few months
are on their
Nikoli Publications page.

A few comments on the books: Puzzle Box is my favorite because it has the
largest variety of puzzles that I can do. The quarterly Puzzle
Communication Nikoli typically includes at least a few brand new types of
puzzles, I'm guessing as tests to see what readers think of them. I think
the best eventually go on to become regularly appearing puzzles. The Penpa
books have the advantage of including rules in English, but often only have
about a dozen different types of puzzles, so it's a bit low in variety.
Most other books Nikoli releases seem to focus on one or a few specific
puzzle types, except for the Puzzle the Giants series, which has a bunch of
types but only large ones, frequently taking up a full page per puzzle. So no matter what your puzzle preferences are, Nikoli's probably got you covered. ;)

Footnotes:[1] I selected these books as my prize for winning
Grant Fikes'
Attack of the Four Puzzles! contest.
[2] I added rules for Dosun-Fuwari, Herugolf, Juosan,
Kurotto, Makaro, Moon-or-Sun, Nagareru, Nurimeizu, Pencils, and Sto-Stone
were added before I tried doing these puzzles, but the source instructions
were in English and from Nikoli. Because of that, I expect that my
summaries here are correct, but I will adjust them if needed once I try some
of these puzzles.